Today, people are living longer than in the past. For retirees, there is a risk that they may outlive their savings. Conventional methods that accumulate savings include individual retirement accounts, 401(k) plans funded from employee paychecks, and Keogh plans for the self-employed. None of these conventional methods provides an assurance that a retired person's savings will last. Even Social Security, a public program in the U.S. that provides lifetime income upon retirement, may fail to keep pace because of economic uncertainties in the early twenty-first century. A few conventional products, such as annuities, offer periodic payments to a person for the life of the person, but these conventional products require a large, upfront financial commitment, and generally lack liquidity.